Non-contacting sensing devices are widely used in a variety of industrial control systems for the detection or measurement of objects such as the movement of products, the motion or position of machine parts and the like. Such devices may be based upon photoelectric sensing, either visible or infrared, ultrasonic sensing, inductive proximity sensing, or other sensing techniques. Regardless of the physical principle relied on for sensing, such sensing devices are generally provided in housings which may be mounted and oriented in places and directions appropriate to the intended application.
For a number of reasons it is desirable to make the sensing device housing modular with two or more modules that may be interconnected together mechanically and electrically to form a complete sensing device. Typically the sensing head is made in a separate module. The sensing head would contain the actual sensing element, for example in the case of a photoelectric control, the sensing head would contain the light transmitting and/or receiving elements. Other functions would be housed in a further module, referred to here for convenience as a control module, to which the sensing head module would attach. The control module may contain other functions such as logic, power load switching, and the like, and it may in turn be broken up into separate modules for those functions. The modular approach offers an advantage in terms of minimizing inventory, as it permits a building block approach so that many different types of sensing heads can be installed on a single body or control module, depending upon specific applications. This greatly simplifies inventory problems, for the manufacturer, distributor and end user.
A further advantage of the modular approach is that it may permit positioning the sensing head on the control module in different directions for different applications. Typically the sensing device is in a generally rectangular housing and means may be provided so that the sensing head can be positioned oriented in any of four possible sensing directions. This permits the control module to be mounted in such a way that allows easy access to its wiring chamber or to adjustments for operating parameters, and the sensing head can be independently positioned to face forward, backward or to either side as required for the application.